Ahead of the Olympics, I’ve written a feature article for Physics World that explores how basilisk lizards and grebes run on water and what it would take for a human runner to do the same. Check it out! (Image credit: B. Mate; see Physics World)
Tag: biology
Wasps in Flight
Personally, I’ve had some bad encounters with wasps, but Dr. Adrian Smith of Ant Lab feels the insects receive short shrift. In this video, he shows many species in the order — most of which are venomless and stingless. In high-speed video, their flight is mesmerizing. Wasps have separate fore- and hindwings, but during flight, they move them like a single wing. Velcro-like hooks on the edges of the wings hold the two together.
From a mechanics perspective, I find this fascinating. Aerodynamically, I’d expect much greater benefits from one large wing over two small ones, but outside of flight, separate wings are more easily tucked away. It’s so neat that wasps have a way to enjoy the benefits of both, enabled by a simple but secure line of hooks. (Video and image credit: Ant Lab/A. Smith)
Fish Ladders Keep Species Swimming
Dams often use fish ladders to help migratory species make their way upstream without interruption. In this video, Grady from Practical Engineering discusses some of the considerations that go into this special infrastructure and what kinds of designs work for different species. The first challenge for any dam is attracting fish to the ladder, which is often done by regulating the water flow at the entrance to create the velocity and turbulence that fish look for when going upstream.
Once fish are in the ladder, they travel up a series of jumps that break the dam’s elevation into manageable steps. Different dams use various baffle designs to create jumps suited to their local species and the way they like to swim. Calmer spots in each section give fish a spot to rest before they carry on. In well-designed systems, the vast majority (97%!) of fish that enter a ladder make it through to the other side. (Video and image credit: Practical Engineering)
Fediverse Reactions
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Sensing Sound Like Spiderwebs
Most microphones — like our ears — work by sensing the tiny pressure changes caused by a sound wave‘s passing. But for microphones built this way, the smaller they get, the more sensitive they are to thermal noise. That’s one reason that the tiny microphones in a laptop or webcam just don’t sound as good as larger mics.
Researchers turned to nature to look for alternative ways to measure sound and zeroed in on the mechanism spiders use. Spiders “listen” to their web’s vibrations; the tiny strands of silk quiver as air flow from a sound moves past. Instead of being pressure-based, this mechanism uses viscous drag to register a sound.
The team fabricated an array of microbeams to test the concept of a viscosity-based microphone and found that tiny beams sensed sounds just as well as larger ones. That means these microphones can get smaller without sacrificing performance. For now, they’re not as sensitive as conventional microphones, but that’s not surprising, given that engineers have been improving pressure-based microphones for 150 years. It’s a promising start for a new technology, though. (Image credit: N. Fewings; research credit: J. Lai et al.; via APS Physics)
“Through the Bubbles”
Many seabirds catch their prey through plunge diving, where they fly to a particular height, then fold their wings, and dive into the ocean. In busy waters, bubbles from all this diving can help obscure the birds from hapless fish. Some birds even use bubbles to escape from their own predators; some penguin species, for example, release trapped air from beneath their feathers as they surface, creating a flurry of bubbles that reduce the drag they have to overcome as they make their exit from the water. The fast exit and bubbly wake help them escape prowling seals. (Image credit: H. Spiers; via BWPA)
Universal Wingbeats
Eagles, butterflies, and whales don’t appear to have much in common, but a new study shows that they — along with over 400 other flying and swimming animals of all sizes — flap with a frequency determined by a simple equation. Their beat frequency is proportional to the square root of their mass divided by their wing area. As you can see in the graph below, this scaling collapses pretty much all of the data onto a single line:
Illustration of the predicted relationship between size and wing frequency (black line) shown alongside various insects, birds, bats, penguins, and whales. The swimming animals also fall on the line, once adjustments are made for the difference in density between air and water. It’s surprising to find such a consistent relationship among animals of such vastly different sizes and types. The next big question for researchers will be unpicking exactly why and how animals evolved to use such a consistent pattern between their size and their wing(/fin) frequency. (Image credit: top – E. Ward, graph – J. Jensen et al.; research credit: J. Jensen et al.; via Physics World)
Building In a Stingless Hive
Honeybees, with their stingers, get lots of attention, but the Americas have plenty of stinger-less honeymakers, too. These stingless bees are native to Mexico, where beekeepers cultivate them for pollination. Without stingers and venom, the bees use their building prowess to keep out unwanted visitors. Much of the hive — from the entrance’s nightly gate to the pods where young are stored — is built from cerumen, a substance the bees create by mixing wax with resins they collect from nearby trees. Just as they do with pollen, worker bees collect drops of resin and store them on their hind legs before flying back to the hive. The viscous fluid sticks well, until a swipe of a leg shears it enough to lower its viscosity and slide it off. (Video and image credit: Deep Look)
Venus Flower Basket Sponges
Venus flower basket sponges have an elaborate, vase-like skeleton pocked with holes that allow water to pass through the organism. A recent numerical study looked at how the sponge’s shape deflects incoming (horizontal) ocean currents into a vertical flow the sponge can use to filter out food.
The sponges’ structure is porous and lined with helical structures. In their simulation, researchers reproduced a version of this structure (shown below) that used none of the real sponge’s active pumping mechanisms. The digital sponge was, instead, purely passive. Nevertheless, the simulation showed that, by their skeletal structure alone, sponges could redirect a significant fraction of incoming flow toward its filtering surfaces. Interestingly, the highest deflection fraction occurred at relatively low flow speeds, showing that the sponges are set up so that their structure is especially helpful for scavenging nutrients from nearly-still waters.
In the real world, these sponges use a combination of passive filtering and active pumping to capture their food, but this study shows that the sponge’s clever structure helps it save energy, especially in tough flow conditions. (Image credit: sponges – NOAA, simulation – G. Falcucci et al.; research credit: G. Falcucci et al.; via APS Physics)
A detail from a numerical simulation shows streamlines around and inside a model sponge. How We Got Atoms From Brownian Motion
In 1827, botanist Robert Brown observed an odd jittery motion of particles as he watched grains of pollen floating in water under his microscope. He saw the random motion also with inorganic — which is to say definitely Not Alive — particles as well. But it was Einstein nearly 80 years later who figured out how to connect this observable motion to atoms. Einstein realized Brown’s particles were being constantly jostled by atomic collisions, and, with a little work, we could use those moving particles to determine Avogadro’s number. Steve Mould walks you through the whole story in this video. (Video and image credit: S. Mould)
“Running on Water”
In the early morning light, young photographer Max Wood captured this coot escaping a fight. With wings flapping, the bird runs across the water surface. Each slap and stroke of a foot provides a portion of the vertical force needed to stay atop the water; lift from its wings provides the rest. With enough speed, the bird will take off. Some birds, however, are born water-walkers; certain species of grebe don’t need to use their wings to run on water. (Image credit: M. Wood; via BWPA)
